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Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-api@vger.kernel.org, Arnd Bergmann , Andy Lutomirski , Balbir Singh , Borislav Petkov , Cyrill Gorcunov , Dave Hansen , Eugene Syromiatnikov , Florian Weimer , "H . J . Lu" , Jann Horn , Jonathan Corbet , Kees Cook , Mike Kravetz , Nadav Amit , Oleg Nesterov , Pavel Machek , Peter Zijlstra , Randy Dunlap , Weijiang Yang , "Kirill A . Shutemov" , John Allen , kcc@google.com, eranian@google.com, rppt@kernel.org, jamorris@linux.microsoft.com, dethoma@microsoft.com, akpm@linux-foundation.org, Andrew.Cooper3@citrix.com, christina.schimpe@intel.com, david@redhat.com, debug@rivosinc.com, szabolcs.nagy@arm.com Cc: rick.p.edgecombe@intel.com Subject: [PATCH v8 28/40] x86: Introduce userspace API for shadow stack Date: Sat, 18 Mar 2023 17:15:23 -0700 Message-Id: <20230319001535.23210-29-rick.p.edgecombe@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20230319001535.23210-1-rick.p.edgecombe@intel.com> References: <20230319001535.23210-1-rick.p.edgecombe@intel.com> X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 49DFA4000C X-Rspam-User: X-Stat-Signature: 65txgkyhe86h6ru54xyy3o5pmxj8fy81 X-HE-Tag: 1679185002-29150 X-HE-Meta: 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 2Kbl5U1M 7eVvzq3yYhYz6PQ076cj3g2QF8etzsSIxKYnidoNjQHWWzQylwuyPDPKcLEV8VuxPQGmwyyqc9FyACj1Mk0yQRfdkqFIVvc4W3MsL1SKbSZQgI2tHsN2hb6LmKiIS3hXhJoLmALpa/KERFeV6qy9VEVq+rfaj08HG04z+m/R0xG8Rew1vKhYl4yOqkxby0lkiQfCr6yYepJTQQhpZpEcDK23n0ssSYFkZJxFowRp9c6JlldOhwQDyG8Y/uIcfGgR15QTsKYF4htlPhDfZ9Roq1TqA5sa1W8DUjqC+3hnGWMOSwUSZh9EXTT0joZu1qi8cH3lmCix0PdfpRuKwHlr799aPSBt66ABMmVya X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Add three new arch_prctl() handles: - ARCH_SHSTK_ENABLE/DISABLE enables or disables the specified feature. Returns 0 on success or a negative value on error. - ARCH_SHSTK_LOCK prevents future disabling or enabling of the specified feature. Returns 0 on success or a negative value on error. The features are handled per-thread and inherited over fork(2)/clone(2), but reset on exec(). Co-developed-by: Kirill A. Shutemov Signed-off-by: Kirill A. Shutemov Signed-off-by: Rick Edgecombe Reviewed-by: Kees Cook Acked-by: Mike Rapoport (IBM) Tested-by: Pengfei Xu Tested-by: John Allen Tested-by: Kees Cook --- This is preparation patch. It does not implement any features. The {} are to make the diff in a future patch cleaner. v8: - Update commit log verbiage (Boris) v4: - Remove references to CET and replace with shadow stack (Peterz) v3: - Move shstk.c Makefile changes earlier (Kees) - Add #ifdef around features_locked and features (Kees) - Encapsulate features reset earlier in reset_thread_features() so features and features_locked are not referenced in code that would be compiled !CONFIG_X86_USER_SHADOW_STACK. (Kees) - Fix typo in commit log (Kees) - Switch arch_prctl() numbers to avoid conflict with LAM v2: - Only allow one enable/disable per call (tglx) - Return error code like a normal arch_prctl() (Alexander Potapenko) - Make CET only (tglx) --- arch/x86/include/asm/processor.h | 6 +++++ arch/x86/include/asm/shstk.h | 21 +++++++++++++++ arch/x86/include/uapi/asm/prctl.h | 6 +++++ arch/x86/kernel/Makefile | 2 ++ arch/x86/kernel/process_64.c | 7 ++++- arch/x86/kernel/shstk.c | 44 +++++++++++++++++++++++++++++++ 6 files changed, 85 insertions(+), 1 deletion(-) create mode 100644 arch/x86/include/asm/shstk.h create mode 100644 arch/x86/kernel/shstk.c diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 8d73004e4cac..bd16e012b3e9 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -28,6 +28,7 @@ struct vm86; #include #include #include +#include #include #include @@ -475,6 +476,11 @@ struct thread_struct { */ u32 pkru; +#ifdef CONFIG_X86_USER_SHADOW_STACK + unsigned long features; + unsigned long features_locked; +#endif + /* Floating point and extended processor state */ struct fpu fpu; /* diff --git a/arch/x86/include/asm/shstk.h b/arch/x86/include/asm/shstk.h new file mode 100644 index 000000000000..ec753809f074 --- /dev/null +++ b/arch/x86/include/asm/shstk.h @@ -0,0 +1,21 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_X86_SHSTK_H +#define _ASM_X86_SHSTK_H + +#ifndef __ASSEMBLY__ +#include + +struct task_struct; + +#ifdef CONFIG_X86_USER_SHADOW_STACK +long shstk_prctl(struct task_struct *task, int option, unsigned long features); +void reset_thread_features(void); +#else +static inline long shstk_prctl(struct task_struct *task, int option, + unsigned long arg2) { return -EINVAL; } +static inline void reset_thread_features(void) {} +#endif /* CONFIG_X86_USER_SHADOW_STACK */ + +#endif /* __ASSEMBLY__ */ + +#endif /* _ASM_X86_SHSTK_H */ diff --git a/arch/x86/include/uapi/asm/prctl.h b/arch/x86/include/uapi/asm/prctl.h index 500b96e71f18..b2b3b7200b2d 100644 --- a/arch/x86/include/uapi/asm/prctl.h +++ b/arch/x86/include/uapi/asm/prctl.h @@ -20,4 +20,10 @@ #define ARCH_MAP_VDSO_32 0x2002 #define ARCH_MAP_VDSO_64 0x2003 +/* Don't use 0x3001-0x3004 because of old glibcs */ + +#define ARCH_SHSTK_ENABLE 0x5001 +#define ARCH_SHSTK_DISABLE 0x5002 +#define ARCH_SHSTK_LOCK 0x5003 + #endif /* _ASM_X86_PRCTL_H */ diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile index 92446f1dedd7..b366641703e3 100644 --- a/arch/x86/kernel/Makefile +++ b/arch/x86/kernel/Makefile @@ -146,6 +146,8 @@ obj-$(CONFIG_CALL_THUNKS) += callthunks.o obj-$(CONFIG_X86_CET) += cet.o +obj-$(CONFIG_X86_USER_SHADOW_STACK) += shstk.o + ### # 64 bit specific files ifeq ($(CONFIG_X86_64),y) diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index bb65a68b4b49..9bbad1763e33 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -514,6 +514,8 @@ start_thread_common(struct pt_regs *regs, unsigned long new_ip, load_gs_index(__USER_DS); } + reset_thread_features(); + loadsegment(fs, 0); loadsegment(es, _ds); loadsegment(ds, _ds); @@ -830,7 +832,10 @@ long do_arch_prctl_64(struct task_struct *task, int option, unsigned long arg2) case ARCH_MAP_VDSO_64: return prctl_map_vdso(&vdso_image_64, arg2); #endif - + case ARCH_SHSTK_ENABLE: + case ARCH_SHSTK_DISABLE: + case ARCH_SHSTK_LOCK: + return shstk_prctl(task, option, arg2); default: ret = -EINVAL; break; diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c new file mode 100644 index 000000000000..41ed6552e0a5 --- /dev/null +++ b/arch/x86/kernel/shstk.c @@ -0,0 +1,44 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * shstk.c - Intel shadow stack support + * + * Copyright (c) 2021, Intel Corporation. + * Yu-cheng Yu + */ + +#include +#include +#include + +void reset_thread_features(void) +{ + current->thread.features = 0; + current->thread.features_locked = 0; +} + +long shstk_prctl(struct task_struct *task, int option, unsigned long features) +{ + if (option == ARCH_SHSTK_LOCK) { + task->thread.features_locked |= features; + return 0; + } + + /* Don't allow via ptrace */ + if (task != current) + return -EINVAL; + + /* Do not allow to change locked features */ + if (features & task->thread.features_locked) + return -EPERM; + + /* Only support enabling/disabling one feature at a time. */ + if (hweight_long(features) > 1) + return -EINVAL; + + if (option == ARCH_SHSTK_DISABLE) { + return -EINVAL; + } + + /* Handle ARCH_SHSTK_ENABLE */ + return -EINVAL; +} -- 2.17.1